Question about 2002 Chevrolet Suburban

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The battery is testing good, 14.37V while idle. As soon as I apply the accelerator the voltage meter connected to the battery gets erratic and the dash voltage meter as well. 2002 Chevy Suburban 5.3 Gas, LS

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Alternator is not working properly.

Posted on Nov 09, 2010

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3 Answers

How do I test the alternator to determine if it's good?


Take the vehicle to a auto parts store , they check them for free .

Apr 21, 2017 | Cars & Trucks

1 Answer

2006 Cadillac CTS help My car was tested @auto zone for the batery n alternator n both passed Good voltage Everytime I go to crank my car it does not crank I have 2 jump it of even if it's for 15 mins


Luis: That makes no sense. But here is what others are saying: " How possible is it for a bad alternator to be tested good? I already had people telling me to replace it.

I got both the battery and alt tested. Both passed.

Reinstalled on the car and it ran good surprisingly after the battery was charged @ the autostore > till after about 10 minutes, then the battery meter dropped back down.

Soon as i turned on the lights/ac the battery meter dripped down real low. SOon as i turned them off the meter jumped back up.


Soon as i revved the engine the headlight would brighten then dim back down after the rev was over.

I can jump the car, but it will turn off by itself if you leave it idling to long then it needs another jump.
Driving it doesn't charge the battery up.. its actually drops the battery meter down more and more and more till its dead.

-Car doesn't drain the battery while its off.. so its nothing left on.


>> Now people are telling me there alternator was tested good, but the problems went away after buying a new alt.
"
Some people say there could be a loose belt not turning the alternator fast enough to supply power to lights/ac and charge battery. Or bad wires". or possibly a bad voltage regulator.

May 28, 2015 | 2006 Cadillac CTS

2 Answers

1993 Trans sport 3800 erratic shifting, idle up and down, CC surges up and down, SEL not on long enough to pull codes. Seems to have started after recent alternator replacement. Shop swapped out ECM and...


Hello! There are a couple of possible solutions...A current surge may have damaged one of the sensors...A multimeter is needed to perform a few test procedures...If you have a meter and a wee bit of experience using it we can test the suspected sensors...The Throttle Positioning Sensor (TPS) is bolted to the Throttle Body...It has a 3 wire connector...Wire colors are...Black...Gray...And Dark Blue...Using 2 safety pins, push the point into the rear of the in-place connector into the Dark Blue wire and into the Black wire...Set the meter to read 5 volts...Connect the +meter probe to the Dark Blue and the - probe to the Black...Start the engine...If you can get the engine to idle for a brief period the meter must read less then 1 volt (.85)...Slowly increase the throttle...The voltage must rise smoothly to 4 volts at full throttle (or as close as you can get)...Point is that the voltage must rise without jumping, jerking or acting erratically...Send a comment with results...If all is well with the TPS we'll move to the next suspect...Picture of TPS is below...Cost is around $50...Guru...saailer

saailer_52.jpg

Dec 27, 2010 | Pontiac Trans Sport Cars & Trucks

3 Answers

After changing fuel pump 2 days ago on my 97 pontiac gtp. it started idling high (2500rpm) then today after getting code p0102(maf sensor) and codes p0122-p0507-p1441 it died on way home and wont start. is...


You can test the MAF before replacing. It may be a problem with the circuit itself or just a fluke from another problem that is connected to this sensor.

There are two basic types of mass airflow sensors: hot wire and hot film. In the first type, a very thin wire (about 0.2 mm thick) is used as the heated element.
f27-31.gif Components of a hot wire-type mass airflow sensor. Courtesy of Ford Motor Company. The element temperature is set at 100° to 200°C above incoming air temperature. Each time the ignition switch is turned to the off position, the wire is heated to approximately 1,000°C for 1 second to burn off any accumulated dust and contaminants.
The second type uses a nickel foil sensor, which is kept 75°C above ambient air temperatures. It does not require a burn-off period and therefore is potentially longer lasting than the hot wire type.
A faulty MAF will cause driveability problems resulting from incorrect ignition timing and improper air/fuel ratios.
Vane-type MAF Sensors
A vane-type MAF sensor is found on many import and domestic vehicles with EFI. All intake air must flow through the sensor. Some MAF sensors are called volume air flow meters
  • Begin checking a vane-type MAF sensor by checking the voltage supply wire and the ground wire to the MAF module before checking the sensor voltage signal.
  • Always follow the recommended test procedure in the manufacturer's service manual and use the specifications supplied by the manufacturer.
  • Typically, to test the sensor, a digital multimeter (DMM) is used and set on a DC voltage scale. The negative meter lead is connected to ground and the red lead to the MAF signal wire.
f_32.44.gif A voltmeter connected to measure the signal from a MAF sensor. Reproduced with permission from Fluke Corporation.
  • Turn on the ignition switch and press the min/max button, if available, on the DMM.
  • Slowly push the MAF vane from the closed to the wide-open position, and allow the vane to slowly return to the closed position.
f_27.33.gif Move the MAF sensor air vane from open to close to test it. Reproduced with permission from Fluke Corporation.
  • Observe the maximum and minimum voltage readings as the vane was moved.
  • If the minimum voltage signal is zero, there may be an open circuit in the MAF sensor variable resistor.
  • When the voltage signal is not within the manufacturer's specifications, replace the sensor.
WARNING While pushing the mass air flow sensor vane open and closed, be careful not to mark or damage the vane or sensor housing.
  • Some vehicle manufacturers specify ohmmeter tests for the MAF sensor.
  • With the MAF sensor removed, connect the ohmmeter across the sensor's output and input terminals.
f_32.45.gif Ohmmeter connections to a MAF sensor. Reprinted with permission.
  • The resistance at these terminals is normally 200 to 600 ohms.
  • Connect the ohmmeter leads to the specified MAF sensor terminals, and move the vane from the fully closed to the fully open position.
  • With each specified meter connection and vane position, the ohmmeter should indicate the specified resistance.
f_32.46.gif Resistance specifications for a typical MAF sensor with door open and closed. Reprinted with permission.
  • When the ohmmeter leads are connected to the sensor's input and output terminals, the ohmmeter reading should increase smoothly as the sensor vane is opened and closed.
  • To check a vane-type MAF with a lab scope, connect the positive lead to the output signal terminal and the negative scope lead to a good ground.
  • This type MAF should display an analog voltage signal when the engine is accelerated. A defective MAF will have sudden and erratic voltage changes.
f_32.47.gif The trace of a defective vane-type MAF sensor. Reproduced with permission from Fluke Corporation. Hot-Wire-Type MAF Sensors
The test procedure for heated resistor and hot-wire MAF sensors varies depending on the vehicle make and year. Always follow the test procedure in the appropriate service manual. A frequency test may be performed on some MAF sensors, such as the AC Delco MAF on some General Motors' products.
  • To check the MAF sensor's voltage signal and frequency, connect a voltmeter across the MAF voltage signal wire and ground wire.
  • Start the engine and observe the voltmeter reading.
  • On some MAF sensors, this reading should be 2.5 volts.
  • Lightly tap the MAF sensor housing with a screwdriver handle and watch the voltmeter pointer.
  • If the pointer fluctuates or the engine misfires, replace the MAF sensor.
  • Some MAF sensors have experienced loose internal connections, which cause erratic voltage signals and engine misfiring and surging.
  • Set the DMM so that it can read the frequency of DC voltage.
  • With it still connected to the signal wire and ground, the meter should read about 30 Hz with the engine idling.
  • Now, increase the engine speed, and record the meter reading at various speeds.
  • Graph the frequency readings. The MAF sensor frequency should increase smoothly and gradually in relation to engine speed.
  • If the MAF sensor frequency reading is erratic, replace the sensor.
f_32..48.gif Satisfactory and unsatisfactory MAF sensor frequency readings. Reproduced with permission from Fluke Corporation.
  • When a scanner is used to diagnose a General Motors' vehicle, one test mode displays grams per second from the MAF sensor. This mode provides an accurate test of the MAF sensor.
  • The grams per second reading should be 4 to 7 with the engine idling.
  • This reading should gradually increase as the engine speed increases.
  • When the engine speed is constant, the grams-per-second reading should remain constant.
  • If the grams-per-second reading is erratic at a constant engine speed or if this reading varies when the sensor is tapped lightly, the sensor is defective.
  • A MAF sensor fault code may not be present with an erratic grams-per-second reading, but the erratic reading indicates a defective sensor.
  • Frequency-varying types of MAF sensors can be tested with a lab scope.
  • The waveform should appear as a series of square waves.
f_32.49.gif A normal trace for a frequency-varying MAF sensor. Courtesy of Progressive Diagnostics--WaveFile AutoPro.
  • When the engine speed and intake air flow increases, the frequency of the MAF sensor signals should increase smoothly and proportionately to the change in engine speed.
  • If the MAF or connecting wires is defective, the trace will show an erratic change in frequency.
f_32.50.gif The trace of a defective frequency-varying MAF sensor. Courtesy of EDGE Diagnostics Systems.

There is also a
Mass Air Flow (MAF) Burn-Off Module Operation:
00375_maf_burn_off_module.jpgA semi-conductor control for an electronic-ignition system.

Nov 17, 2009 | Pontiac Grand Prix Cars & Trucks

1 Answer

2000 ford zx2, battery light keeps coming on/off, had alt checked (good), battery checked (good), could this possibily be a wiring issue (short/bad connection)?


There seems to be a no charge state in this case. i recommend checking the charging system. use the procedure below to isolate this issue.

Wear protective eye wear and clothing and remove all jewelry when checking your battery and charging system. Jewelry is a good conductor of electricity and is not recommended. Most batteries wear out every 3 to 5 years and need to be replaced. Always replace your battery with an equal replacement battery to assure proper operation. Automotive batteries have a +positive terminal (red), - negative terminal (black). Electricity is stored in the battery and then supplied to the vehicle when the engine is not running. While the engine is running the vehicles alternator charges the battery for future use. (Note: never disconnect the battery while the engine is running. If the battery cable is disconnected from the battery a spark can be generated which can cause the battery to explode or a major electrical malfunction to occur.)

To check a battery surface voltage, remove the positive terminal protective cover. Connect the +positive side meter lead (red) to the positive side battery terminal. Connect the - negative (black) side meter lead to the negative battery terminal. With the vehicle not running and the car sitting over night the battery voltage should be between 12.5 and 12.8 volts.(You will need to use a voltmeter for this testing procedure)

The alternator is rotated by a drive belt driven by the vehicles engine while it is running. Electrical voltage and amperage are generated to recharge the battery and supply voltage to the electrical system of the car. The alternator is held in place with mounting bolts. There is a main electrical wire on the rear of the alternator that supplies voltage to a main voltage junction box. If your alternator is not charging properly, your battery will slowly drain down from operating all the electrical systems in your car and stop the car from running.(most non charge states will be the cause of a loose belt or a low tension rate, due to a mis-adjusted alternator. make sure you have enough tension in the belt for full rotation of the alt pulley)

Next, you will need to check the alternators output with the Amp meter.

Testing the amperage output of the alternator is good for measuring the amount (not the level) of voltage the alternator can produce. This test can be tricky because if the alternator is weak it can still show it as producing amperage. Which is good, but if the voltage is low, it will still allow the battery to go dead. To check the amperage output of an alternator an amp meter is needed. Once the meter is connected start the engine. Next turn on all electrical accessories and raise the engine idle to about 1200 RPM. The alternator should output the max amperage it was designed to produce. Example: a 90 amp alternator should output about 88 amps. Note: An alternator cannot sustain maximum output for long periods of time. If the alternator is forced to operate at maximum output it will overheat and fail. An alternator is designed to operate at max amperage output only for a reasonable amount of time.

((Connect the voltage meter lead the same way you would in a battery static voltage check, Start engine (do not drive) at engine idle the voltage should be between 13.6 to 14.3 volts. If not the alternator may need replacing.)))

Nov 02, 2009 | Ford ZX2 Cars & Trucks

1 Answer

New battery when i turn on the heat. my battery light came on? why


The alternator should be tested for its operational value in this case. There may be some issues with the charge rate.

Testing the amperage output of the alternator is good for measuring the amount (not the level) of voltage the alternator can produce. This test can be tricky because if the alternator is weak it can still show it as producing amperage. Which is good, but if the voltage is low, it will still allow the battery to go dead. To check the amperage output of an alternator an amp meter is needed. Once the meter is connected start the engine. Next turn on all electrical accessories and raise the engine idle to about 1200 RPM. The alternator should output the max amperage it was designed to produce. Example: a 90 amp alternator should output about 88 amps. Note: An alternator cannot sustain maximum output for long periods of time. If the alternator is forced to operate at maximum output it will overheat and fail. An alternator is designed to operate at max amperage output only for a reasonable amount of time.

((Connect the voltage meter lead the same way you would in a battery static voltage check, Start engine (do not drive) at engine idle the voltage should be between 13.6 to 14.3 volts. If not the alternator may need replacing.)))

Oct 08, 2009 | 1999 Ford Contour

1 Answer

87 300zx maf dianostic test --need ohms test or electrical test


test for voltage with key on check all wires with digital meter only set to 5 or 10 volts dc base and digonsotic voltage is as follows 1.5 is base 5 is test lotage hook up the ground wire and tesy with a vachum pump as you apply vachum 18 inchs voltage should rise to max 4.5 volts as vac is let off should drop to 1.5 a steady needle indactes it's ok if it is erratic replace the unit.

Jul 19, 2009 | Nissan 300ZX Cars & Trucks

2 Answers

1997 Cadillac Catera: When the AC is on and the cooling fan comes on the charging guage drops to almost the red. voltage at battery drops from 14.6 to 13.2 and shows undercharge on a battery testing meter....


A charge rate of 13.2 is fine...Likely your battery is getting older and is not charging as well as it used to. You should periodically re-charge the battery using an external charger, as the alternators actual function is to maintain the batteries state of charge, not to re-charge it. Opening the doors, playing the radio with the engine off etc, can and will drain your battery. The alternator will only put a surface charge there and will not actually replace this lost power. I'd begin to worry if charge rate dropped below 12.9.but even then you likely would not have any real problems.

Jul 16, 2009 | 1997 Cadillac Catera

1 Answer

Voltage drop test


First, check battery post to cable connection: positive meter lead on battery positive post, negaitve lead on battery's positive cable clamp. Crank the engine and note the reading. A good connection should have zero voltage drop. Second, check the positive cable: positve meter lead on positive battery clamp, negative lead on starter terminal connector. A good cable will show a voltage drop of .2 volts or less while cranking. Third, check the starter connection: positive meter lead on positive battery terminal on the solenoid, negative meter lead on actual starter stud. A good connection will have a voltage drop of near zero volts. Now to check the negative side of the circuit. Total drop on the ground side should be .3 volts or less and can be checked by placing positive meter lead on starter housing and negative meter lead on battery ground post. Take your reading while cranking the engine, and be sure your connection at the starter is solid and clean. If total voltage drop on this side of the circuit is excessive, complete testing at all connections in the same fashion as the positive side of the circuit. Check the following: between battery post and clamp (zero voltage drop), cable end at battery to cable end at engine. (.2 volts or less), cable end at engine to engine itself (near zero voltage drop), and finally between starter housing and engine block (.1 volts or less).

To read the entire procedure for all automotive systems read this artile:
http://www.engine-light-help.com/voltage-drop.html

Aug 31, 2008 | 1997 Chevrolet Blazer

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